Re: kmem-pool-uvm

On 11/03/2011 02:02 AM, Mindaugas Rasiukevicius wrote:
> Hello Lars,
>
> Sorry for late reply.
>
> Lars Heidieker <lars%heidieker.de@localhost> wrote:
>>>> i uploaded a new version of the kmem-pool-vmem-uvm patch:
>>>> ftp://ftp.netbsd.org/pub/NetBSD/misc/para/kmem-pool-vmem-uvm.patch
>>>>
>> <...>
>>
>> I've uploaded a new Version of the patch and a small patch that
>> replaces malloc with kmem in the ufs/ext2 (mainly) readdir code as
>> those allocation were (due to blocksize) 4k which made them just too
>> large with the malloc-header for the max 4k caches currently
>> implemented in the patch.
>
> Thanks, I think the changes in essence are great and we should have
> them for netbsd-6. Few comments:
>
> - Having IPL_VM lock for kmem(9) can increase masking of interrupts and
> given that we want to reduce allocations from the interrupt context,
> it is not really desirable. However, there is a long way to go and at
> this point I think it is not a problem, since kmem cache layer will
> minimise the use of the lock.
>
> - As already said, in the long term we want to minimise memory allocations
> from the interrupt context. With kmem(9) becoming interrupt-safe, there
> is a potential for abuse. I think that the general purpose kmem_alloc(9)
> and kmem_free(9) routines should explicitly prohibit calls from interrupt
> context by keeping the asserts on !cpu_intr_p() and !cpu_softintr_p().
> For this purpose, there can be e.g. kmem_intr_alloc()/kmem_intr_free(),
> so we would have strict interface level separation preventing for abuse.
> It would also be easier to find such allocations from interrupt-context.
>
> - I would leave uvm_km_alloc/free() interface naming as is and instead of
> heap_va_arena would have something similar to old, e.g. kmem_va_arena.
> Also, perhaps s/heap_meta_arena/kmem_va_meta_arena/.
>
> - From bt_refillglobal:
>
> + if (vmem_alloc(heap_meta_arena, PAGE_SIZE,
> + (flags & ~VM_FITMASK) | VM_INSTANTFIT | VM_POPULATING, &va) != 0)
> {
> + return ENOMEM;
> + }
>
> Error path leaks vmem_btag_lock.
>
I've uploaded a new version of the kmem-pool-vmem-uvm patch:
ftp://ftp.netbsd.org/pub/NetBSD/misc/para/kmem-pool-vmem-uvm.patch
It incorporates some enhancements and makes the talked about interrupt
safe version private to malloc(9) and fixes the leakage of vmem_btag_lock.
Lars
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